Due to developments in the last one to two decades in flexible fabrics, such as nylon, dacron, etc., it has become possible to fabricate flexible doors for very large openings such as aircraft hanger doors. These doors typically include a flexible curtain secured at its top to an overhead member and a roller secured generally at the bottom of the curtain with a means for raising and lowering the door by winding or unwinding it upon the roller. Such a door is disclosed in commonly owned U.S. Pat. No. 3,398,779. Such doors if properly constructed have the requisite strength to withstand wind forces, are resistant to damage, and yet require relatively little storage space when in an upper rolled position. Although such a flexible door in its closed position will withstand high wind pressures, the lack of a good seal, in addition to slackness of the curtain, causes substantial air leakage, undesirable flapping and permits the possibility of unwanted entry. The leakage and flapping is caused by the tendency of the flexible door to billow under strong wind pressures.
Other sealing means have been developed for flexible doors such as disclosed in commonly owned U.S. Pat. No. 3,704,742. However, the sealing means disclosed therein does not assist in the elimination of wrinkles on the roller when it is wound thereon and also may permit slack when unwound. As a result, especially with the larger doors, wind acts upon the curtain slack in causing flapping which still results in breakage of the seal in some cases, and decreases the useful life of the curtain by facilitating stretch and tear.